Container carriers such as port cranes, rubber tyred gantry cranes (RTG), shuttle carriers, straddle carriers or transporting carriers are used in ports and terminals for transporting cargo containers. Great quantities of containers are to be unloaded, placed in intermediate storage and reloaded for another mode of transportation.
The ship to shore crane, STS, lifts containers for loading and unloading ships. The movement of the port crane is usually limited to rails. The straddle carrier or transporting carrier transports containers between the port crane and a storage area. The freely moving container carrier operates in the cargo handling area. One major risk involved with such freely moving carriers is falling over. This may occur when the loading and unloading of the vessel must be done as quickly as possible. Any additional delays and disturbances result in extra costs by having ships idle in the berth, and even more so if the loading/unloading is for some reason delayed, thus making the ship late in her route schedule.
The stability of the container carrier, such as a straddle carrier, needs to be improved to avoid any accidents. Speed limits in certain areas could lead to slower handling of the cargo. In addition, freely moving container carriers have no specific routes; instead, operators may choose any appropriate route to the destination using the free area in the port or terminal field.